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The effective utilization of slag fertilizer in agriculture to neutralize soil acidity, improve crop productivity, mitigate greenhouse gas emissions, and stabilize heavy metals in contaminated soils turns it into a high value added product in sustainable agriculture. These effects could be due to the shift in microbial metabolism and/or modification of microbial habitats. At the system level, soil microorganisms play an integral role in virtually all ecosystem processes. There is a growing interest to reveal the underlying mechanisms of slag-microbe interactions and the contribution of soil biota to ecosystem functioning. In this perspective, we discuss the possible driving mechanisms of slag-microbe interactions in soil and how these slag-microbe interactions can affect crop yield, greenhouse gas emissions, soil carbon sequestration, and heavy metal stabilization in contaminated soils. In addition, we discuss the problems and environmental concerns in using slag in agriculture. Emphasis has been given for further research to validate the proposed mechanisms associated with slag-microbe interactions for increasing soil quality, crop productivity, and mitigating environmental consequences. While evaluating the slag amendment, effects on agriculture and environment, the potential risks, socio-economics, techno-economics, and ethics should be assessed.

Co-composting of organic wastes is globally recognized to be effective method to dispose two or more wastes at once and minimize drawbacks of composting such as gases emissions and nutrient reduction. In this study, pilotscale experiments were conducted to characterize the co-composting process of chicken manure with cow manure (CC), swine manure (CS), plant residues plus mushroom media (CRM), on emissions of greenhouse gas, and ammonia, compost quality, maturity and their correlations. The results showed that cumulative flux of carbon dioxide (CO 2), methane (CH 4), nitrous oxide (N 2 O) and ammonia (NH 3) widely ranged like 38,211-50,830, 172-417, 98-142 and 118-927 g kg dm −1 day −1 respectively. It indicated the importance of selection for co-composting material. The NH 3 emission was significantly increased by 4.3-7.9 times in CS and CRM, compared to OC and CC. Both of CS and CRM also showed longer thermophilic phase and later maturation were also observed in both treatments. Temperature was positively correlated with gases (P < 0.001) except CH 4 , and nitrogen content, C/N ratio and nitrate nitrogen significantly affected emission of carbon and nitrogen (P < 0.001). In conclusion, for chicken manure composting, sole chicken manure or combination with cow manure could be suitable composting method to improve compost quality and minimize gases losses.

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